<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>window对象</title>
</head>
<body>

</body>
<script>

    var rnd = window.Math.random();
    var rnd2 = Math.random();
    alert(rnd);

    window.str = "hello";



</script>
</html>